In recent years, mouse and human induced pluripotent stem cells (iPS cells) have been successively established. Yamanaka et al., have induced iPS cells by introducing Oct3/4, Sox2, Klf4, and c-Myc genes into mouse-derived fibroblasts so as to enable the forced expression of such genes (WO 2007/069666 A1 and Takahashi, K. and Yamanaka, S., Cell, 126: 663-676 (2006)). Subsequently, it has been revealed that iPS cells can also be prepared using 3 of the above factors (excluding the c-Myc gene) (Nakagawa, M. et al., Nat. Biotechnol., 26: 101-106 (2008)). Furthermore, Yamanaka et al., have succeeded in establishing iPS cells by introducing the 4 above genes into human skin-derived fibroblasts, similarly to the case involving mice (WO 2007/069666 A1 and Takahashi, K. et al., Cell, 131: 861-872 (2007)). Meanwhile, Thomson et al.,'s group has prepared human iPS cells using Nanog and Lin28 instead of Klf4 and c-Myc (WO 2008/118820 A2 and Yu, J. et al., Science, 318: 1917-1920 (2007)). iPS cells can solve bioethical issues such as embryo disruption, and can be grown while maintaining their pluripotency, so that iPS cells are expected as grafting materials for regenerative medicine.
Meanwhile, even when the thus established iPS cells are induced to differentiate into specific tissue cells, the resulting cells may include undifferentiated (or insufficiently differentiated) cells having proliferation potency (Miura K. et al., Nat Biotechnol., 27: 743-745 (2009)). In such a case, there are concerns about tumorigenesis after grafting. Hence, a method for screening for an iPS cell line containing no cells that exhibit resistance to differentiation induction from among the thus established iPS cell lines has been desired.